A system-on-a-chip (SoC) is an integrated circuit (IC) that integrates many or all components of a computer or other electronic system into a single chip. A typical SoC comprises many functional units, which may include microprocessors, memory blocks, timing sources, peripherals such as counter-timers, and external interfaces such as Universal Serial Bus (USB) port and an Ethernet port. Each functional unit requires configuration access and debug access in order to enable its operation. During various phases of a design cycle, different functional units may be added, dropped, or relocated. As a consequence, the configuration scheme can become complicated and delicate, and often requires the involvement of the entire design team.